In addition, the MathWorks have so far managed not too screw up too badly and are keeping Matlab up to date. (They are definitely quite nice as an employer.)
I've heard this argument a lot (since 1999), but I'm not confident it holds true anymore. The free alternatives are so good.
You may be right regarding Professors, but that is also changing as they age out.
Could be; we don't use Matlab much in my own research area, so recent change could've happened under my radar. When I've occasionally had contact with engineers in industry, though, Matlab still seemed to be everywhere. The most recent two examples were someone doing DSP, and someone doing mechanical engineering, and both had all their stuff built on top of Matlab+Simulink.
In my area of CS (artificial intelligence) it seems considerably less popular. I don't really remember how to use it, since the last time I used it seriously was in some engineering (but not CS) courses in undergrad.